Citizen Science for Soil Monitoring and Protection in Europe: Insights from the PREPSOIL Project Under the European Soil Mission

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors!

The manuscript is devoted to the important problem of verification and detailing of remote sensing data for monitoring the ecological condition of soil cover with the assistance of Citizen Science. The authors consider a large pool of information sources and analyze the effectiveness of various tools used by volunteers and professional operators/researchers for this. This is relevant in the context of sustainable land management and environmental security. The subject of the manuscript is relevant both for the region of study and for other regions. There are a number of important comments. I recommend the authors correct the text of the manuscript.

1. The title of the manuscript does not fully correspond to its content. The authors discuss exclusively the European experience of involving Citizen Science. Therefore, it is necessary to either supplement the manuscript with data from other regions or make adjustments in the title of the article, in the Abstract and in the Introduction Section, and also explain why the research is limited to European Citizen Science.
2. The manuscript is positioned as a review. Therefore, I recommend that the authors expand the list of sources. Namely, in the Introduction Section to give at least a brief reference: (1) on the place of the European experience of involving Citizen Science in monitoring the soil cover state/health on a global scale, (2) on the motivation of citizens to participate in such activities, and (3) on the place of this type of research in the overall structure of Citizen Science.
3. Sections “2. Materials and Methods” and “3. Results” begin with introductions, in which the following information is summarized. This arrangement of material is appropriate for a report or presentation, not for an article. I recommend that the authors modify the text of these parts, namely in the introduction to the Section “2. Materials and Methods” to set out a general concept and in the introduction to the section “3. Results” to detail which of the results were received by the authors and which exclusively by literature and other sources.
4. In the Section “2. Materials and Methods,” it should be clearly stated what the authors used as objects (materials) to carry out analysis and obtain results given in the following section.
5. In the Section “3. Results,” the results should be separated from the discussion, which is not relevant to this Section; it should be moved to the next Section. Since the article is positioned as a review, it seems acceptable to combine Sections “3. Results” and Section “4. Discussion” into one Section “Results and Discussion”. Emphasis should be placed on information obtained directly by the authors of the manuscript.
6. On P.4, l.162-163, the "Collected Citizens Science Database" is presented as a table, which is named as Figure 1.
7. Figure 2 (P.5) shows data for Spain twice.
8. The text (P.11, l.441-446) discusses Table 2, while below (P.11, l.447-448) is a table entitled “Figure 6. Respondents’ satisfaction with existing methods of soil monitoring”.
9. (P.12, l.480-486) The thesis “The subsequent sections delve into these barriers in greater detail, framing the study's observations within established soil-monitoring frameworks and proposing pragmatic recommendations for policymakers, practitioners, and community leaders seeking to expand or refine citizen science initiatives in soil health [1, 39]. By addressing these constraints systematically, stakeholders can further harness the strengths of citizen-driven data collection, ultimately contributing to more robust, inclusive, and actionable soil monitoring practices”, as a conclusion on the Section “3. Results” is inappropriate in the context of the review article.
10. (P.12, l.489-496) The thesis “The findings presented in this study highlight both the opportunities and complexities of using citizen science for soil monitoring. They build on a growing body of literature demonstrating that volunteer-based data collection can significantly augment spatial and temporal coverage, enhance public engagement, and inform policy decisions at multiple governance levels [31, 13, 48]. The diversity of soil health indicators—ranging from organic carbon and nutrient levels to biodiversity and pollutant concentrations—emphasizes the multifaceted nature of soil management and underscores the need for adaptable yet robust monitoring frameworks [9, 26]” should be placed at the end of the Section “4. Discussion”, not at the beginning as an introduction.
11. (P.14-15, l.573-600) It is recommended structuring The Section “5. Conclusions” in accordance with the objectives stated in the Introduction Section (P.2, l.83-87).

Author Response

We sincerely thank the reviewers for their constructive and detailed feedback, which has helped to improve the clarity, structure, and scholarly contribution of our manuscript. Below we provide a point-by-point response to all reviewer comments. All changes have been incorporated into the revised manuscript, and line references refer to the marked-up version where applicable.

For research article “sustainability-3631549”

Response to Reviewer 1 Comments

Comments 1: The title of the manuscript does not fully correspond to its content. The authors discuss exclusively the European experience of involving Citizen Science. Therefore, it is necessary to either supplement the manuscript with data from other regions or make adjustments in the title of the article, in the Abstract and in the Introduction Section, and also explain why the research is limited to European Citizen Science.

Response 1: We sincerely thank Reviewer 2 for the thoughtful and specific comments. Below we provide a point-by-point response, indicating how each comment was addressed in the revised manuscript. Line references correspond to the marked-up version. We fully agree with the reviewer’s observation, and we have made corresponding revisions to improve the clarity, methodological transparency, and overall quality of the manuscript.

To ensure the title accurately reflects the manuscript’s scope and institutional context, we have revised it to explicitly delimit the geographic focus on Europe. The updated title reads:
“Citizen Science for Soil Monitoring and Protection in Europe: Insights from the PREPSOIL Project under the European Soil Mission.”

This change aligns the title with the study’s European framework and avoids potential misinterpretation regarding its global applicability.

The Abstract has been revised to clearly state that the findings are based exclusively on European experiences. It now emphasizes that the study draws on data collected by the PREPSOIL project, specifically through literature review, project inventories, and stakeholder engagement across five Living Labs located in different European countries. The final sentence of the Abstract was updated to note that the research is situated within the framework of the European Soil Mission, highlighting the policy context and geographic scope.
The Introduction (pp. 1–2) has been modified to (i) clearly establish the European orientation of the study, (ii) introduce the PREPSOIL project as the core foundation of the manuscript, and (iii) explicitly state that the geographic limitation to Europe reflects the mandate and scope of the project. This clarification appears in the closing paragraph of the Introduction, providing justification for the regional focus in alignment with EU research priorities and the European Soil Mission.

Comments 2: The manuscript is positioned as a review. Therefore, I recommend that the authors expand the list of sources. Namely, in the Introduction Section to give at least a brief reference: (1) on the place of the European experience of involving Citizen Science in monitoring the soil cover state/health on a global scale, (2) on the motivation of citizens to participate in such activities, and (3) on the place of this type of research in the overall structure of Citizen Science.

Response 2: We have substantially revised the second half of the Introduction (pp. 2–3) to address all three requested dimensions, supported by recent and relevant scholarly literature.

Global perspective: We now highlight that the European experience represents one of the most policy-integrated and institutionally supported models of citizen science in soil monitoring, while also referencing comparable practices in global contexts (e.g., Mason et al., 2024; Danielsen et al., 2014; Geo-Wiki, GROW[50, 52, 57]). These additions underscore both the distinctiveness and the transferability of the European approach.

Citizen motivation: The revised paragraph discusses key motivational drivers—such as environmental concern, co-creation, educational value, and perceived societal relevance—drawing from empirical studies (Serret et al., 2019; Price et al., 2024; Gardiner et al., 2012[53, 55, 54]). We emphasize that long-term engagement, regular feedback, and capacity-building activities are critical to sustaining volunteer participation and ensuring data quality (Mason et al., 2024; Schacher et al., 2023[52, 56]).

Structural placement within citizen science: We have added references that contextualize soil-related initiatives within broader citizen science domains such as biodiversity monitoring and public health. While participation in soil monitoring is increasing, it remains underrepresented compared to other thematic areas. Typologies and overviews (Head et al., 2020 [51]) are now cited to clearly position this field within the larger CS ecosystem.

This new paragraph reflects a synthesis of high-quality global sources, including systematic reviews, comparative analyses, and program-level evaluations. The corresponding citations have been added to the revised manuscript and full reference list. We trust these enhancements provide greater analytical depth and directly address the reviewer’s recommendation.

Comments 3: Sections “2. Materials and Methods” and “3. Results” begin with introductions, in which the following information is summarized. This arrangement of material is appropriate for a report or presentation, not for an article. I recommend that the authors modify the text of these parts, namely in the introduction to the Section “2. Materials and Methods” to set out a general concept and in the introduction to the section “3. Results” to detail which of the results were received by the authors and which exclusively by literature and other sources.

Response 3: We thank the reviewer for this constructive suggestion and fully agree that clarifying the conceptual framing and source attribution enhances the scientific structure of the manuscript.

Section 2 has been retitled “General Concept and Methodological Framework”. A new introductory paragraph has been added to articulate the overarching research concept, namely, the evaluation of citizen science as a complementary mechanism for soil monitoring within the policy context of the European Soil Mission. The section now systematically outlines the study’s mixed-methods approach, including review of literature, analysis of European project documentation, digital tool inventory, the PREPSOIL database of 96 initiatives, and original empirical data from stakeholder workshops and surveys.

Section 3 has been retitled “Results: Empirical Insights and Evidence from Literature.” The introductory paragraph was revised to clearly distinguish between (i) results generated through the authors’ own empirical work (e.g., PREPSOIL database compilation, questionnaire analysis, Living Labs) and (ii) findings synthesized from secondary sources (peer-reviewed studies, grey literature, public databases). Each subsection in Section 3 follows this distinction to maintain transparency and methodological integrity.

These changes enhance the article's structure and improve alignment with the expectations for a peer-reviewed research review.

Comments 4: In the Section “2. Materials and Methods,” it should be clearly stated what the authors used as objects (materials) to carry out analysis and obtain results given in the following section.

Response 4: We appreciate the reviewer’s comment highlighting the need for greater clarity regarding the analytical materials employed. In response, we have revised the beginning of Section 2.1, now under the heading “General Concept and Methodological Framework”, to explicitly identify and describe the five categories of materials analyzed in the study:

Peer-reviewed and grey literature;

Documentation from relevant European projects;

Citizen science digital tools and platforms;

A structured PREPSOIL database of 96 initiatives;

Empirical stakeholder inputs, including questionnaire responses and data from Living Lab workshops.

These materials constitute the core evidence base and are analyzed using a combination of qualitative and quantitative methods, which are detailed in the corresponding subsections of the methodology. We believe this revision fully addresses the reviewer’s concern and improves the transparency of the analytical design.

Comments 5: In the Section “3. Results,” the results should be separated from the discussion, which is not relevant to this Section; it should be moved to the next Section. Since the article is positioned as a review, it seems acceptable to combine Sections “3. Results” and Section “4. Discussion” into one Section “Results and Discussion”. Emphasis should be placed on information obtained directly by the authors of the manuscript.

Response 5: We thank the reviewer for this important and constructive suggestion. In response, we have restructured Sections 3 and 4 by merging them into a single unified section titled “Results and Discussion.” This revised structure aligns with the expectations for a review article and improves the coherence between empirical insights and interpretative synthesis.

Within the new section, we have revised both subheadings and narrative flow to clearly distinguish between:

Primary findings generated directly by the authors (e.g., PREPSOIL database analysis, stakeholder survey data, Living Lab outputs); and

Secondary findings derived from literature synthesis or analysis of external project materials.

This restructuring enhances the article’s clarity and evidentiary transparency while maintaining a logical and reader-friendly format.

Comments 6: On P.4, l.162-163, the "Collected Citizens Science Database" is presented as a table, which is named as Figure 1.

Response 6: Thank you for pointing out this inconsistency. We have corrected the labeling: the structure of the Collected Citizen Science Database is now presented as Table 4, while Figure 1 now correctly refers to the country-level distribution of initiatives. All figure and table numbers have been reviewed and adjusted throughout the manuscript to ensure consistency and accuracy.

Comments 7: Figure 2 (P.5) shows data for Spain twice.

Response 7: Thank you for catching this error. The duplicated entry for Spain in Figure 2 has been removed, and Spain now appears only once with a unified value of 8 initiatives. The corrected figure has been updated and is included in the revised manuscript.

Comments 8: The text (P.11, l.441-446) discusses Table 2, while below (P.11, l.447-448) is a table entitled “Figure 6. Respondents’ satisfaction with existing methods of soil monitoring”.

Response 8: We thank the reviewer for noting this discrepancy. The visual element in question is a figure (not a table), and the reference in the main text was incorrectly labelled as Table 2. We have corrected the manuscript to properly reference this output as Figure 6 in the relevant paragraph. This ensures consistency between the in-text citation and the caption. Additionally, we have reviewed all figure and table references throughout the manuscript to confirm accuracy and prevent similar inconsistencies.

Comments 9: (P.12, l.480-486) The thesis “The subsequent sections delve into these barriers in greater detail, framing the study's observations within established soil-monitoring frameworks and proposing pragmatic recommendations for policymakers, practitioners, and community leaders seeking to expand or refine citizen science initiatives in soil health [1, 39]. By addressing these constraints systematically, stakeholders can further harness the strengths of citizen-driven data collection, ultimately contributing to more robust, inclusive, and actionable soil monitoring practices”, as a conclusion on the Section “3. Results” is inappropriate in the context of the review article.

Response 9: Thank you for this valuable observation. We agree that the statement in question was more interpretive in nature and thus better suited for the discussion or synthesis section rather than the end of the Results. In response, we have removed the paragraph from the end of Section 3.8 and relocated the relevant content, after appropriate revision, to Section 4.1 (“Cross-cutting Challenges and Enabling Factors”), where it now supports the broader interpretive analysis and policy relevance of the findings. This change improves the structural clarity of the manuscript and ensures that results are clearly separated from analytical synthesis and conclusions, in accordance with the review article format.

Comments 10: (P.12, l.489-496) The thesis “The findings presented in this study highlight both the opportunities and complexities of using citizen science for soil monitoring. They build on a growing body of literature demonstrating that volunteer-based data collection can significantly augment spatial and temporal coverage, enhance public engagement, and inform policy decisions at multiple governance levels [31, 13, 48]. The diversity of soil health indicators—ranging from organic carbon and nutrient levels to biodiversity and pollutant concentrations—emphasizes the multifaceted nature of soil management and underscores the need for adaptable yet robust monitoring frameworks [9, 26]” should be placed at the end of the Section “4. Discussion”, not at the beginning as an introduction.

Response 10: We thank the reviewer for this helpful recommendation. In response, we have relocated the interpretative statement, originally positioned at the beginning of the discussion, to the conclusion of the relevant subsection (now Section 4.1: Cross-cutting Challenges and Enabling Factors). This adjustment ensures that the paragraph now functions as a synthesizing reflection based on preceding empirical and thematic content, rather than as a general introductory statement. All associated references [9,13,26,31,48] have been retained. We agree that this revision improves the logical flow and strengthens the structural clarity of the discussion.

Comments 11: (P.14-15, l.573-600) It is recommended structuring The Section “5. Conclusions” in accordance with the objectives stated in the Introduction Section (P.2, l.83-87).

Response 11: We have revised the Conclusion (Section 5) to clearly reflect the three main objectives stated in the Introduction. The structure now follows a three-part logic:

Summary of contributions to scientific knowledge;

Summary of key implementation findings;

Policy and methodological recommendations.

We believe these changes fully address the reviewer’s concern and improve the internal consistency of the manuscript.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This article addresses a critical environmental issue pertaining to the soil health and shows how everyday people (citizens) can help monitor it. The comments of this reviewer is as under:

• Figure 1 Collected Citizens Science Database is almost unreadable.
• What quantitative metrics (e.g., RMSE, R², accuracy) were used to validate citizen-collected data against expert or sensor-based benchmarks?
• Were normality, multicollinearity, or sampling adequacy (e.g., KMO test) assessed before applying PCA to project attributes?
• What kind of training or instructions do volunteers receive before collecting soil data?
• Can the data from different countries and tools be easily combined, or are there compatibility issues?
• Which soil properties (e.g., pH, organic carbon) are most commonly measured by citizen scientists, and why?
• Do authors consider heavy metal contamination in soil which play a critical health issues in recent times. For insance, https://doi.org/10.1016/j.scitotenv.2023.161468.
• There are some grammatical mistakes.

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

We sincerely thank the reviewers for their constructive and detailed feedback, which has helped to improve the clarity, structure, and scholarly contribution of our manuscript. Below we provide a point-by-point response to all reviewer comments. All changes have been incorporated into the revised manuscript, and line references refer to the marked-up version where applicable.

For research article “sustainability-3631549”

Response to Reviewer 2 Comments

We sincerely thank Reviewer 2 for the thoughtful and specific comments. Below we provide a point-by-point response, indicating how each comment was addressed in the revised manuscript. Line references correspond to the marked-up version.

Comments 1: Figure 1 Collected Citizens Science Database is almost unreadable.

Response 1: We agree that the original figure was difficult to read. The table has now been reformatted for clarity and moved to the Annex 1 as Table A1, while the visual data distribution has been clarified in the new Figure 1 (showing initiative count per country). Labels, font sizes, and layout have been revised for publication readability.

Comments 2: What quantitative metrics (e.g., RMSE, R², accuracy) were used to validate citizen-collected data against expert or sensor-based benchmarks?

Response 2: Thank you for this important question regarding data validation. As clarified in the revised manuscript, our study is a narrative and quantitative synthesis of existing citizen science projects and does not involve primary fieldwork or instrument deployment. The accompanying Excel file serves as a descriptive register of initiatives, detailing aspects such as geographic location, monitored parameters, and engagement models. It does not include columns for validation metrics such as RMSE, R², or accuracy. We have added two sentences to the manuscript to explicitly state this scope limitation and to mention the specific validation metrics that were occasionally reported in the original studies. This clarification addresses the concern while remaining consistent with the available evidence and the stated aims of our paper.

Comments 3: Were normality, multicollinearity, or sampling adequacy (e.g., KMO test) assessed before applying PCA to project attributes?

Response 3: Thank you for raising this methodological point. We have clarified in the Methods and Discussion sections that the PCA was used as an exploratory tool applied to publicly available metadata from 96 citizen science initiatives. Prior to extraction, we assessed sampling adequacy (KMO = 0.71) and confirmed factorability using Bartlett’s test (p < 0.001). To address multicollinearity, we removed one variable pair with a correlation exceeding |r| > 0.85. Given the binary and ordinal nature of the input variables, we also relaxed the multivariate normality assumption by employing a tetrachoric correlation matrix instead of Pearson correlations. These additions directly address the concern and enhance the transparency of our analytical approach.

Comments 4: What kind of training or instructions do volunteers receive before collecting soil data?

Response 4: Thank you for highlighting this important aspect of citizen science practice. As noted in the revised manuscript, our study is a scoping review and does not include original field campaigns. The accompanying Excel register documents high-level attributes such as geography, monitored parameters, and validation approaches, but does not contain a dedicated column for volunteer training. We have added clarifying sentences to the manuscript to explain that information on training is fragmentary in the source materials. Where reported, instructions range from written guidelines and workshops to app-based tutorials. These additions acknowledge the reviewer’s point while remaining consistent with the scope and available data of our review.

Comments 5: Can the data from different countries and tools be easily combined, or are there compatibility issues?

Response 5: Our article is a scoping review; we did not pool or statistically harmonize raw soil measurements from different countries. Instead, the PREPSOIL project compiled a standardized Excel-based register of 96 citizen science initiatives, capturing metadata such as the presence or absence of open licensing and adherence to interoperability standards. These binary indicators revealed that while several widely used tools (e.g., FotoQuest Go, iNaturalist, Geo-Wiki) support open data practices, the majority of local and regional projects still disseminate outputs in proprietary formats or without clear licensing terms. This heterogeneity in data accessibility and format is precisely why openness and interoperability were queried during database construction, and why the limitations of cross-country integration are explicitly acknowledged in our manuscript.

Comments 6: Which soil properties (e.g., pH, organic carbon) are most commonly measured by citizen scientists, and why?

Response 6: Our review synthesises metadata only; no primary soil samples were collected. Frequencies quoted above derive from the PREPSOIL database fields “Soil pH”, “Soil-organic-carbon”, and “Soil-structure/texture”. The questionnaire results from five Living Labs independently corroborate this ranking (soil biodiversity 75 %, organic carbon 55 %, structure 55 %, nutrients 55 %). These insertions stress both which properties dominate volunteer monitoring and why they do so, thereby addressing the request without implying new empirical measurements

Comments 7: Do authors consider heavy metal contamination in soil which play a critical health issues in recent times. For insance, .

Response 7: Heavy-metal contamination is considered in our review. The Excel register contains a binary field “Focus on presence of soil pollutants” that covers heavy metals; 21 initiatives flag this field as “yes” and 16 as “partly”.

The manuscript already mentions heavy-metal monitoring in the literature review and key-observation sections

Comments 8: There are some grammatical mistakes.

Response 8: Thank you for pointing this out. We thoroughly proofread the entire manuscript and corrected all grammar, clarity, and formatting issues. This includes removing duplicated words, correcting verb tenses, and polishing long sentences. The language has now been reviewed for publication quality.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1. Figure 1 is completely unreadable.
2. This manuscriptreflects on the role of citizen science in soil monitoring and protecting through a literature review, but does not use bibliometric methods and lacks quantitative analysis methods.
3. Cluster analysis in bibliometrics can be used to reflect current research hotspots and future research trends in citizen science in soil monitoring and conservation.
4. Figure 2 proposes the use of a world map to show the geographical distribution of citizen science initiatives.
5. What is Figure 3 trying to convey?
6. In Part 2.5, some indicate that a questionnaire was used, what was the content of the questionnaire? What results does the questionnaire reflect?
7. It is recommended that more practical examples be included to demonstrate the effectiveness of the implementation of citizen science policy recommendations in soil monitoring and protection, especially those specific to different regions.

Author Response

We sincerely thank the reviewers for their constructive and detailed feedback, which has helped to improve the clarity, structure, and scholarly contribution of our manuscript. Below we provide a point-by-point response to all reviewer comments. All changes have been incorporated into the revised manuscript, and line references refer to the marked-up version where applicable.

For research article “sustainability-3631549”

Response to Reviewer 3 Comments

We sincerely thank Reviewer 3 for the constructive and insightful feedback. Your comments were instrumental in helping us refine the manuscript, particularly in terms of methodological clarity, visual presentation, and the contextual depth of our analysis. We fully agree with your observations and have carefully addressed each point in the revised version. Below, we provide a detailed point-by-point response outlining how your suggestions were incorporated into the manuscript.

Comments 1: Figure 1 is completely unreadable.

Response 1: We agree. The original version of Figure 1 has been replaced with a fully redesigned and high-resolution bar chart (p. 10), showing the number of initiatives per country. Font sizes, spacing, and color contrast have been optimized for readability in both print and online formats. In addition, the full structure of the underlying database is now presented as Table A1 in the Annex, improving overall transparency.

Comments 2: This manuscript reflects on the role of citizen science in soil monitoring and protecting through a literature review, but does not use bibliometric methods and lacks quantitative analysis methods.

Response 2: We appreciate this observation. While the original scope of the paper was primarily qualitative and integrative, we now explicitly clarify this limitation in the Introduction and Section 2.1. Given the nature of the PREPSOIL project and the types of data collected (e.g., initiative inventories, stakeholder workshops), traditional bibliometric clustering techniques were not applicable. However, we have added references to bibliometric studies (e.g., Odenwald, Bedessem) in Section 2.1 and expanded the thematic classification of initiatives in Tables 1–3 to reflect analytical structure.

Comments 3: Cluster analysis in bibliometrics can be used to reflect current research hotspots and future research trends in citizen science in soil monitoring and conservation.

Response 3: We appreciate the suggestion. While cluster or co-citation analysis was beyond the methodological scope of this paper, we now reference such methods as a future direction in Section 4.3. Specifically, we acknowledge that bibliometric clustering could be used in subsequent work to map emerging research trends and policy-relevant subdomains in soil-related citizen science.

Comments 4: Figure 2 proposes the use of a world map to show the geographical distribution of citizen science initiatives.

Response 4: Thank you for this recommendation. As our study focuses on European initiatives only (due to the scope of the PREPSOIL project), a global map would not reflect data coverage accurately. However, the newly revised Figure 1 now presents a geographically grouped bar chart that aligns visually with the reviewer’s suggestion and improves spatial clarity.

Comments 5: What is Figure 3 trying to convey?

Response 5: Thank you for this clarification request. We acknowledge that the original Figure 3 lacked clarity. This figure has been revised to better illustrate the scale of citizen science initiatives (local, regional, national, etc.) based on the PREPSOIL database. All labels and percentage values now reflect corrected proportions and are accompanied by a clear explanatory caption. This figure now appears as Figure 2 in the revised manuscript.

Comments 6: In Part 2.5, some indicate that a questionnaire was used, what was the content of the questionnaire? What results does the questionnaire reflect?

Response 6: We thank the reviewer for this important question. We have significantly expanded the explanation of the questionnaire content and its empirical relevance in Section 2.6 and Section 3.6 of the revised manuscript.

The questionnaire focused on key themes including:

Prior engagement in citizen science projects;

Preferred soil-health indicators (e.g., biodiversity, organic carbon, pH, structure);

Perceptions of data quality and validation requirements;

Satisfaction with different soil monitoring methods (remote sensing, in situ, citizen science);

Needs related to training, feedback, and equipment access.

As now detailed in the manuscript, quantitative results from 20 respondents revealed:

Most frequently selected indicators: soil biodiversity (75%), soil organic carbon (55%), and nutrient levels (55%);

60% of participants rarely or occasionally collected soil data;

Satisfaction levels with existing methods are summarized in Table 7;

Four recurring challenges were identified: lack of harmonized protocols, insufficient spatial coverage, limited access to low-cost equipment, and time constraints.

These insights, gathered from stakeholders in five Living Labs, have been incorporated into the results and are further interpreted in the discussion to illustrate practical barriers and enablers for citizen science in soil monitoring. We believe this clarifies the empirical role of the questionnaire and its contribution to the overall findings.

Comments 7: It is recommended that more practical examples be included to demonstrate the effectiveness of the implementation of citizen science policy recommendations in soil monitoring and protection, especially those specific to different regions.

Response 7: Thank you for this valuable recommendation. We have revised the manuscript to include a broader range of practical, region-specific examples demonstrating how citizen science contributes to policy and land management outcomes.

A new subsection (Section 3.6) has been added, summarizing five illustrative case studies from across Europe: LandSense (Austria), LUCAS Photo Module (EU-27), CurieuzeNeuzen (Flanders), Maaiveld (Netherlands), and ECHO (Czech Republic, France, Spain). Each example highlights a clear link between citizen-collected soil data and a tangible policy response or management practice.

In addition, Section 4.2 and Section 5 have been revised to further emphasize the implementation impact of these initiatives. These additions include:

The use of citizen data by local authorities for soil sealing restrictions;

The integration of CS-generated indicators into the Common Agricultural Policy (CAP) framework;

The application of CS data in regional erosion control planning.

We also discuss the mediating role of Living Labs and digital tools (e.g., Geo-Wiki, LandSense) in translating citizen-generated evidence into actionable policy processes. We trust these revisions provide concrete and geographically diverse examples that align with the reviewer’s request.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear colleagues,
The authors have made all necessary edits. The article can be published in its current form.

Author Response

We sincerely thank Reviewer 1 for their time and favorable assessment of our manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors

Accept!

Author Response

We sincerely thank Reviewer 2 for their time and favorable assessment of our manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript reflects on the role of citizen science in soil monitoring and protecting through a literature review, but does not use bibliometric methods and lacks quantitative analysis methods. Cluster analysis in bibliometrics can be used to reflect current research hotspots and future research trends in citizen science in soil monitoring and conservation.

Author Response

Comment:
This manuscript reflects on the role of citizen science in soil monitoring and protecting through a literature review, but does not use bibliometric methods and lacks quantitative analysis methods. Cluster analysis in bibliometrics can be used to reflect current research hotspots and future research trends in citizen science in soil monitoring and conservation.

Response:

“This manuscript reflects on the role of citizen science in soil monitoring and protecting through a literature review, but does not use bibliometric methods and lacks quantitative analysis methods. Cluster analysis in bibliometrics can be used to reflect current research hotspots and future research trends in citizen science in soil monitoring and conservation.”

We appreciate the reviewer’s recommendation and have implemented a comprehensive bibliometric component, integrated into the revised Section 2.2 (“Literature review and bibliometric analysis”, pp. 4–6). Key additions are summarised below.

1. Corpus and software. A consolidated Boolean query was applied to Scopus and Web of Science (5 May 2025), yielding 182 unique records (2000–2025). Full records were processed with the bibliometrix R package (v 4.3).
   
   
2. Quantitative descriptors. The analysis reports publication growth (compound annual rate = 11.2 %), source and geographic productivity, and an overall corpus h-index of 34.
   
   
3. Cluster analysis. A co-word network (Keywords Plus, frequency ≥ 5) was partitioned by Louvain modularity optimisation (modularity Q = 0.41; silhouette = 0.72). Four stable clusters were identified:
   C1 Biogeochemical indicators and degradation processes;
   C2 Citizen-science design and data-quality assurance;
   C3 Earth-observation integration;
   C4 Soil-related biodiversity assessment.
   
   
4. Trend detection. Five-year temporal slicing highlights an historical focus on remote-sensing validation (2008–2015) and a recent acceleration (post-2019) of topics such as soil biodiversity, microplastics, and machine learning.
   
   
5. Integration with other quantitative work. The bibliometric results now triangulate with (i) the classification of forty core references (Tables 1–3), (ii) the statistical inventory of 96 European CS initiatives (Section 3.5), and (iii) stakeholder-survey metrics from five living labs (Section 3.7). The manuscript therefore combines qualitative synthesis with multiple quantitative analyses, as requested.
   
   

We trust that these revisions fully address the reviewer’s concerns regarding the use of bibliometric and quantitative methods and the identification of current hotspots and future research trends.

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

Part “Theoretical clustering and temporal trends” is recommended to present this section in the form of a graph.

Author Response

Comments 1: Part “Theoretical clustering and temporal trends” is recommended to present this section in the form of a graph.

Response 1:

Thank you for your valuable suggestion to present the section "Theoretical clustering and temporal trends" in graphical form. In response, we have added Figure 1, titled "Temporal distribution of thematic clusters in citizen-science soil literature (2000–2024)", which visually represents the evolution of key thematic areas over time.

The accompanying text (see page 5-6) highlights the main temporal patterns and transitions observed in the data. This includes the early dominance and later decline of EO-integration studies (C3), the steady rise of biogeochemical themes (C1), the post-2010 acceleration in design and QA-related research (C2), and the emergence and stabilization of biodiversity topics (C4) after 2005.

We believe this graphical addition enhances the clarity and interpretability of the trends discussed and aligns well with your recommendation. Thank you for helping us improve the manuscript.

Author Response File: Author Response.docx